1. Field of the Invention
The present invention relates to a semiconductor device, and more specifically to a plasma etching apparatus and a plasma etching method.
2. Description of the Background Art
In a plasma etching apparatus, a focus ring is used for controlling plasma in the vicinity of the circumference of a wafer. Thereby, an etching rate at the circumferential area of the wafer is controlled. Also, it has been known that the etching rate at the circumferential area of the wafer depends on a height of the focus ring.
However, the focus ring is exposed to plasma during etching. Therefore, when an etching apparatus is used for a long period of time, the focus ring is corroded by an etching gas, and a height of the focus ring changes.
Thereby, the etching characteristics change at the circumferential area of the wafer, and a uniformity of the etching rate on the surface of the wafer becomes worse.
Also, the focus ring must be replaced every time after a certain number of wafers have been processed, and consequently there was a problem of increasing running costs of a dry-etching apparatus.
The present invention has been conceived to solve the previously-mentioned problems and a general object of the present invention is to provide a novel and useful plasma etching apparatus and to provide a novel and useful plasma etching method.
A more specific object of the present invention is to maintain the etching rate at the circumferential area of the wafer constant without replacing any focus ring.
The above object of the present invention is attained by a following plasma etching apparatus and a following plasma etching method.
According to one aspect of the present invention, the plasma etching apparatus comprises: a lower electrode supporting a semiconductor substrate; a focus ring disposed along a circumference of the semiconductor substrate; a sensor for measuring a position of an upper surface of the focus ring; a drive mechanism for driving the focus ring vertically; and a controller for adjusting the position of the upper surface of the focus ring by driving the drive mechanism on the basis of a result of measurement by the sensor.
According to another aspect of the present invention, the plasma etching method comprises; a measurement step of measuring an upper surface of a focus ring; an adjustment step of adjusting a position of the upper surface of the focus ring by driving the focus ring vertically on the basis of the result of measurement by the measurement step; and an etching step of performing etching after finishing the adjustment step.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.